Change Detection in Nutrients, Chlorophyll, Phytoplankton Composition and Primary Production Terry E. Whitledge and Sang H. Lee Institute of Marine Science, University of Alaska Dept. of Oceanographic Science, University of Pusan RUSALCA PI Meeting St. Petersburg, Russia May 2013

CS8 CEN4 LS1 LS3 SS5 SS4 WN3 WN1 HC49 HC24 HC60 GD7 CL1 CL3 CL7A CL6 CS1 CS4 CS12 CS16 Primary Production Stations on Leg 2

Two different size communities of phytoplankton psu 32.5 psu A>20 µm 5 µm <B<20 µm 0.7 µm <C<5 µm A (94 %) B (3 %) C (3 %) A (42 %) B (18 %) C (40 %) 32.5 psu Lee et al. (2007)  Depending on different water masses, there were two different communities of phytoplankton in the Chukchi Sea in 2004

CS8 CEN4 LS1 LS3 SS5 SS4 WN3 WN1 HC49 HC24 HC60 GD7 CL1 CL3 CL7A CL6 CS1 CS4 CS12 CS16 Compositions of small phytoplankton (<20 μm) Pico and Nano Prochlorococcus Synechococcus 69.8% 21.4% 8.8% 66.9% 14.5% 18.6% Pico and Nano Prochlorococcus Synechococcus In 2009, synechococcus and prochlorococcus species were found among small phytoplankton communities (<20um) in our study sites. These species were limited in the Arctic cold waters. But, recently water temperatures in the Chukchi Sea (next slide) have increased up to 5 C in this region. So, these species could survive !

Macromolecular compositions of phytoplankton (averaged from 3 water depths, 100, 30, and 1% at each station) Proteins Polysaccharides Lipids LMWM BSL3 ST10 A3 ST14 PHL12 Lee et al. (2009) High protein production  Low nitrogen stress?  In general, phytoplankton produced more proteins than other macromolecular compositions such as lipids, Polysaccharides, and LMWM, which indicates that phytoplankton might not have a nitrogen limitation in the Chukchi Sea. This is an interesting result since phytoplankton especially in the Alaskan Costal Water were characterized as having nitrogen limitation before.

Bering Sea Chukchi Sea Alaska Russia B04 B10 B14 B21 B26 B40 B42 C04 RC03 C09 C14 C16 C26 C22 C29 Station locations for 2007 Oshoro Maru cruise. Triangles show productivity stations

PO 4 SiO 4 NH 4 NO 3 southern Bering Sea northern Bering Sea central Chukchi Sea northern Chukchi Sea mmole/m2 Integrated nutrients in euphotic zone

southern Bering Sea northern Bering Sea central Chukchi Sea northern Chukchi Sea mg/m2 Integrated chlorophyll in euphotic zone

Bering Sea Chukchi Sea Alaska Russia B04 B40 RC B10 B14 B21 B26 B42 C04 C09 C14 C16 C26 C22 C29 mg C m -2 h -1

Bering Sea Chukchi Sea Alaska Russia B04 B B10 mg N m -2 h -1 B14 B21 B26 B42 C09 C22 C26 C29 RC03 C04 C14 C16

Light intensity (%) Carbon uptake rate (h -1 ) Bering Sea Chukchi Sea

Injected nitrate concentration (µM) Carbon uptake rate (h -1 ) Bering Sea Chukchi Sea

Bering Sea Chukchi Sea Alaska Russia B14 B04 B B10 B26 B42 C09 C C04 RC03 C16 C26 C22 C29 C14 B21 f-ratios

Continuing measurement for Primary Productivity in the Chukchi Sea  Recent productivity is ~3 times lower than decade(s) ago in the Chukchi Sea! Lee et al. (2007)Lee et al. (2013) Lee et al. (2012) Lee et al. (in preparation)

Source Productivity Method Place or Water mass Season (g C m -2 day -1 ) McRoy et al. (1972) C uptake western Being Strait June Hameedi (1978) C uptake Chukchi Sea July > 3.0 central Chukchi Sea Sambrotto et al. (1984) 2.7 NO 3 - disappearance western Being Strait Springer (1988) C uptake central Chukchi Sea 11 July-2 August Korsak (1992) C uptake Chukchi Sea 28 July-31 August Zeeman (1992) C uptake Chukchi Sea 28 July-31 August 0.8 Bering Strait Hansell et al. (1993) NO 3 - disappearance Anadyr Water in the north of Bering Strait Springer and McRoy C uptake and central Chukchi Sea 28 July-31 August (1993) chl-a concentration Hill and Cota (2005) C uptake northeastern Chukchi Sea summer Lee et al. (2007 ) C uptake Chukchi Sea August 1.4 central Chukchi Sea Primary Productivity  Recent productivity was ~3 times lower than decade(s) ago in the Chukchi Sea!

Primary Productivity in the Chukchi Sea, 2012 (RUSALCA) HC2 G12 CEN1A CEN4 HC26 CS17 CS8 CL8 CL3R CL5A 20 mg C m -2 h -1 Alaska Russian Chukchi Sea Average ± S.D.= 27.9 ± 34.8 mg C m -2 h -1  2012 productivity in the Chukchi Sea was still 3 times lower than decade(s) ago!

NEC5 NWC5 NWC4 NEC3 SIL3 NWC3 SIL2 ANSC NOM5 NOM1 SPH1 MK2 RUS4 BRS-A5 NWC2 SWC4 KIV2 KNG1 SEC mg C m -2 h -1 Recent PP in the N Bering Sea, 2007  120 g C m -2 y -1 (this study in 2007) g C m -2 y -1 (Hansell and Goering 1990; Springer and McRoy 1993; Springer et al. 1996) Lee et al. (2012)  Consistent 2-3 times lower productivity in the Northern Bering Sea!

Conclusions. Phytoplankton – smaller size classes appear to have increased Chlorophyll – integrated biomass decreased by 40% Primary Production – rates are reduced 2-3 fold since 1980’s Hypothesis: Large phytoplankton are growing fast enough to reduce the nutrient concentrations to low levels. Zooplankton are grazing on large phytoplankton leaving some of the small ones. Low chlorophyll values represent the remains from grazing and the low biomass produces the small primary production rates.